Method of spacing the plates of a gaseous discharge device

ABSTRACT

A pair of glass plates of a gaseous discharge display or memory device are held precisely spaced by two sets of identically sized overlapping spacer rods. The rods crisscross orthogonally within a sealed gas-containing chamber to create gaps through which the gas can flow without significant restriction between areas of the chamber separated by said rods. Sealing rods of glass having a softening temperature lower than that of the spacer rods are disposed like a border around the spacer rods and are of significantly greater diameter or height than the combined height of the two superposed sets of spacer rods. Initially the upper plate is supported solely by sealing rods; but upon heating of the assemblage, the sealing rod glass reflows, and the upper plate settles until it contacts the upper set of spacer rods; whereupon the assembly is cooled and the sealing rods fuse with the plates to create an impermeable chamber between the now precisely spaced plates.

United StatesPatent [1 1 Costa et a1.

14 1 Jan.7, 1975 METHOD OF SPACING THE PLATES OF A InternationalBusiness Machines Corporation, Armonk, N.Y.

Filed: Oct. 18, 1973 Appl. No.: 407,770

Related [1.8. Application Data Division of Ser. No. 251,483, May 8,1972, Pat. No. 3,808,497.

[73] Assignee:

US. Cl. .1 29/25.13 Int. Cl. .Q H0lj 9/18 Field of Search 29/2513;316/19, 20;

References Cited UNITED STATES PATENTS 3,602,754 8/1971 Pfaender et al315/169 R X 3,602,756 8/1971 Bonnet 315/169 R X 3,778,127 12/1973Langston, Jr. et a1. 316/20 Primary Examiner-Gerald A. Dost AssistantExaminer-James W. Davie [57] ABSTRACT A pair of glass plates of agaseous discharge display or memory device are held precisely spaced bytwo sets of identically sized overlapping spacer rods. The rodscrisscross orthogonally within a sealed gas-containing chamber to creategaps through which the gas can flow without significant restrictionbetween areas of the chamber separated by said rods. Sealing rods ofglass having a softening temperature lower than that of the spacer rodsare disposed like a border around the spacer rods and are ofsignificantly greater diameter or height than the combined height of thetwo superposed sets of spacer rods. Initially the upper plate issupported solely by sealing rods; but upon heating of the assemblage,the sealing rod glass reflows, and the upper plate settles until itcontacts the upper set of spacer rods; whereupon the assembly is cooledand the sealing rods fuse with the plates to create an impermeablechamber between the now precisely spaced plates.

4 Claims, 4 Drawing Figures l A ,I/ I I I I I I z I 18 r I 1 I PatentedJan. 7, 1975 3,858,284

2 Sheets-Sheet 1 Patented Jan. 7, 1975 3,858,284

2 Sheets-Sheet 2 FIG. 3

14 10 A 12 16kL -L 11/18 (D 1 a n/ \O 20 METHOD OF SPACING THE PLATES OFA GASEOUS DISCHARGE DEVICE This application is a division of applicationSer. No. 251,483 now US. Pat. No. 3,808,497 filed May 8, 1972 entitled,Gaseous Discharge Device and Method of Spacing The Plates Thereof,assigned to the assignee of the present invention.

CROSS-REFERENCE TO RELATED APPLICATIONS US. Pat. application of R.Langston et al., Ser. No. 214,298, filed Dec. 30, 1971, now US. Pat. No.3,778,127, entitled Sealing Technique for Gas Panel," assigned to theassignee of the present invention.

BACKGROUND OF THE INVENTION This invention relates to gas dischargedisplay and/or memory devices, and more particularly to improved devicesof this type embodying a method of spacing the plates with spacerelements that do not inhibit flow of gas particles between areasseparated by such spacer elements.

In the above-referenced copending application of R. Langston et al.,there is disclosed a gaseous discharge display device in which thesuperposed glass plates are accurately spaced apart using a combinationof lowsoftening-point sealing rods and high-softening-point spacer rods.The large diameter sealing rods are orthogonally arranged in a windowframe-like border around the significantly smaller diameter orthogonallyarranged single layer of spacer rods. When the plates and rods areheated, the glass of the sealing rods reflows, causing the upper glassplate to settle gradually into contact with the high-softening-pointspacer rods for accurately spacing the upper plate relative to the lowerplate. When the assembly is cooled, the sealing rods fuse to the plates,creating a chamber of precise constant height into which an illuminablegas is later introduced and sealed.

This device and method are very satisfactory where the area of theplates is relatively small and the spacer rods need only frame thedisplay area. However, as the plate area and hence the display area areincreased,

' spacer rods must be introduced at other intermediate locations withinthe chamber to maintain the critical precise spacing between the plates.In such case, the spacer rods can extend only a short distance in eitherdirection because wherever they are present (except at the edges of thedisplay area) they present a barrier. This barrier impedes the flow ofgas particles, metastable ions, photons, etc., between adjacent areasseparated by the spacer rods; and it can also inhibit conditioning ofcells, especially those immediately adjacent the spacer rods.

There is a need for a spacing arrangement that will provide accuratespacing of glass plates in gaseous discharge devices having largedisplay areas requiring spacers at various places within the displayarea as well as around the periphery thereof. It would also be desirableto minimize the size of the spacer elements for aesthetic reasons sothey will not be visible and mar the display area, and at the same timeprovide greater latitude in their location.

SUMMARY OF THE INVENTION Toward this end, and according to theinvention, applicants have found that these objectives can be achievedby an improved gaseous discharge display and/or memory device and methodwhich, insofar as is known, have never heretofore been proposed. In thisdevice and according to applicants improved spacing method, the platesare held precisely spaced at a prese lected constant distance by twosets of identically sized crisscrossing spacer rods disposedorthogonally with respect to each other in overlapping lattice-likecontact within the sealed gas-containing chamber. The spacer rods of oneset contact the dielectric coating over the parallel conductors on oneof the plates; and the spacer rods of the other set contact thedielectric coating over the orthogonally arranged parallel conductors onthe other plate. Since these spacer rods have diameters equal to onlyone-half of said preselectd constant distance, flow of gas particlesbetween areas separated by the spacer rods is not significantly impeded.The spacer rods associated with the conductors on each plate aredisposed between, and extend parallel to, the conductors on thatparticular plate. The diameters of the spacer rods preferably varybetween approximately 0.002 inch and 0.0037 inch, according to which ofthe embodiments, hereinafter described, is employed.

Other objects and advantages will become apparent from the followingmore detailed description of the invention and from the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic perspectiveview, partly broken away, of a gaseous discharge display deviceembodying the invention;

FIG. 2 is a fragmentary sectional view, to substantially enlarged scale,taken along the line 2-2 of FIG. 1, showing a preferred embodiment ofthe invention;

FIG. 3 is a sectional view, to somewhat exaggerated scale, showing theassemblage before a heat fusion step that results in the configurationshown in FIG. 2; and

FIG. 4 is a fragmentary sectional view, similar to FIG. 2, but showingan alternate embodiment of the invention.

DESCRIPTION OF PREFERRED EMBODIMENT The gaseous discharge display and/ormemory device constructed according to this embodiment and illus tratedin FIGS. 1-3 comprises, briefly, an upper glass plate 10 and a lowerglass plate 11, each including substrates 12,13, respectively, on thefacing surfaces of which are formed passivated metalized conductorarrays 14,15, respectively. As illustrated, the arrays 14,15

each comprise respective pluralities of parallel conductors, theconductors of array 14 being disposed orthogonally relative to those ofarray 15. The ends of the array on each plate extend beyond the edges ofthe other plate to facilitate connection to alternate conductors of thearray, in conventional manner. As best shown in FIGS. 2,3, theconductors of each array 14,15 are overlaid with respective transparentdielectric coatings 16,17, preferably of glass, which provide flatsurfaces 18,19, respectively.

The plates 10,11 are fused into an integrated structure in the followingmanner. Unfused, heat-fusible sealing material, preferably in the formof rods 20 of low-softening-point glass, are placed in a windowframeborder-like pattern on surface 19 of lower plate 11. These rods 20 areof an identical diameter that is significantly greater than the precisepreselected distance at which these plates are ultimately to be joined.

According to the invention, two sets of identically sized upper andlower spacer rods 21,22 are then placed in overlaying relation in atwo-stratum crisscross pattern within the border. The lower rods 22extend parallel to, and are equidistantly spaced between, adjacent pairsof conductors in array and rest on flat surface 19; whereas upper rods21 overlay and rest on lower rods 22 in a predetermined lateral spacinghereinafter to be described. As will be noted from FIG. 3, the combinedheight of the overlapped rods 21,22 is substantially less than thediameter of the sealing rods 20.

The upper plate 10 is now positioned over the lower plate 11 with upperplate surface 18 contacting sealing rods 20 and transversely positionedsuch that the upper spacer rods 21 extend parallel to, and equidistantfrom, but substantially below, pairs of adjacent conductors of array 14(as a result of the aforesaid predetermined spacing of rods 21 on rods22). Rods 21,22, which are preferably formed of glass, have,asignificantly higher softening point than that of the sealing rods.Hence, when the unfused assemblage of discrete parts is thereafterheated in a vacuum oven to a temperature sufficient to cause melting andreflow of the sealing material of rods 20, upper plate 10 will graduallysettle from the position shown in FIG. 3 until surface 18 contacts upperspacer rods 21, as shown in FIG. 2;

The assemblage is now permitted to cool, causing the now reflowedsealing material, designated 20' in FIG. 2, to fuse to the surfaces18,19 of the respective dielectric layers 16,17 and thereby fuse plates11 into an integrated structure having an impermeable chamber 23 sealedabout its periphery by the material 20. In accordance with conventionalpractice, this chamber 23 is now evacuated via an exhaust tube 24 (FIG.1), then charged with an illuminable gas at appropriate pressure;whereupon the tube is sealed to permanently entrap the gas within thechamber.

It will thus be seen that according to a feature of the invention, theplates will be maintained at a precise preselected distance by thecrisscross pattern of overlapping spacer rods 21,22. Because thesespacer rods have a diameter which is equal to only one-half of the totalconstant space between the surfaces 18,19, the gas particles, metastableions, protons, etc., may flow without significant restriction betweenthe various areas into which the chamber 23 is separated by the latticearrangement of spacer rods.

In the preferred embodiment illustrated in FIG. 2, the sealing rods 20preferably have a diameter of about 0.040 inch, and the spacer rods21,22 preferably have a diameter of approximately 0.002 inch; anddielectric coatings 16,17 have a softening temperature which is abovethe temperature to which the assemblage is subjected during theabove-described fusing operation so that the rods 21,22 will contact,but not penetrate, the dielectric surfaces 18,19. With this arrangement,the small size of the spacer rods renders them substantiallyindistinguishable from the glass plates and hence is aestheticallydesirable. Also, blocking of the display area at the crossover points ofthe respective rods 21,22 is minimized by spacing these rods betweenconductors so as not to blank out any appreciable illumination uponfiring of cells comprised of conductors adjacent to these rods.

DESCRIPTION OF ALTERNATE EMBODIMENT The device and sealing methodemployed according to this embodiment (see FIG. 4) are identical withthose already described in connection with the embodiment of FIGS. 1-3,except in the following respects: According to the instant embodiment,the upper and lower spacing rods 2l',22, respectively, are of somewhatlarger diameter, such as 0.0037 inch; and the coatings 16,17' are of adielectric having a softening temperature which is below the temperatureto which the assemblage is heated during the fusing process. As aresult, the spacer rods 2l',22 will penetrate the dielectric coatingsuntil they contact the surfaces of the respective substrates 12,13. Thusthe constant spacingbetween the plates will be defined by respectivecontacts of the spacer rods 21',22 with the substrates rather than withthe dielectric coatings; however, the actual constant height of thechamber 23 will still be that corresponding to the precisely fixedspacing between the flat portions of surfaces 18',19'.

It is to be understood that the conductor configuration and composition,the specific oven structure and temperatures used for the fusingoperation, and the apparatus by which the chamber 23 is evacuated andthen charged with illuminable gas may be as taught in the prior art,such as the above-referenced Langston et al. application; and hence theyhave not been described here in any more detail than is necessary for anunderstanding of the present invention.

While the invention has been shown and described with reference topreferred'embodiments thereof, it will be understood that varioussubstitutions and changes in form and detail may be made by thoseskilled in the art without departing from the spirit and scope of theinvention. Accordingly, the gas discharge display and/or memory deviceherein disclosed and the method of making same are to be consideredmerely as illustrative, and the scope of the invention is to be limitedonly as specified in the claims.

What is claimed is:

1. A method of sealing flat surfaces of two members in overlyingrelation at a precise preselected distance to create an impermeablechamber of constant height 1 divided into areas by spacer elements thatdo not significantly impede flow of gas between such areas in thechamber, comprising the steps of providing two substantially transparentflat members,

each said member having parallel conductors overcoated with a thin layerof dielectric material, placing on one of the members a border ofunfused heat-fusible material having a height significantly greater thansaid constant height, placing spacer elements of substantially identicalthickness in a two-stratum crisscross pattern within said border to acombined height significantly less than the minimum height of saidmaterial, placing the other member with its flat surface supported onsaid heat-fusible material, and heating such assemblage to a temperatureabove the softening point of said sealing material but below thesoftening point of the spacer elements to effect fusion of said materialand members to create said chamber as, and in consequence of, said othermember settling during such heating and fusing until it is supported atsaid constant height by said crisscrossed arrangement of spacerelements. 2. A method of making a gaseous discharge display device,comprising the steps of providing two substantially transparent flatmembers,

each with conductor arrays overcoated with a dielectric material,

placing unfused heat-fusible sealing material over the dielectricmaterial on one of the members as a frame-like border enclosing themajor portion of its conductor array, said border having a height substantially greater than the final constant spacing desired between saidmembers,

disposing two sets of spacer elements of identical height between themembers to create an assemblage in which the elements orthogonallyoverlap in a lattice-like relation within the bordered area, elements ofone set resting on said one member and supporting overlying elements ofthe other set, the combined thickness of both sets of elements beingsubstantially less than the height of said border so that said othermember is initially supported by the sealing material, and

heating the assemblage to a temperature above the softening point ofsaid sealing material but below the softening point of the spacerelements to effect fusion of said sealing material and members to createan impermeable chamber for confining a prede termined volume of gas,said other member settling during such heating and fusing until it issupported at said final constant spacing by said lattice arrangement ofoverlapping elements to permit the gas to fiow without significantrestriction to substantially all areas of said sealed member separatedby said spacer elements.

3. The method according to claim 2, wherein the conductors of eachmember are disposed orthogonally to the conductors of the other member,and

spacer elements of said one set are disposed equidistant between, andextend parallel to, pairs of adjacent conductors on the said one member,and

spacer elements of said other set are disposed equidistant between, andextend parallel to, pairs of adjacent conductors on said other member.4. A method of making a gaseous discharge display device, comprising thesteps of providing two transparent flat members, each with conductorarrays formed on a substrate and overcoated with a layer of a dielectricmaterial,

placing unfused heat-fusible sealing material over the dielectricmaterial on one of the members as a frame-like border enclosing themajor portion of its conductor array, said border having a heightsubstantially greater than the final constant spacing desired betweensaid members,

disposing two sets of spacer elements of identical height between themembers to create an assemblage in which the elements orthogonallyoverlap in'a latticelike relation within the bordered area, elements ofone set resting on the layer of said one member and supporting overlyingelements of the other set, the combined thickness of both sets ofelements being substantially less than the height of said border so thatsaid other member is initially supported by the sealing material, and

heating the assemblage to a temperature above the softening point ofsaid sealing material and dielectric material but below the softeningpoint of the spacer elements to effect fusion of said sealing materialand members to create an impermeable chamber for confining apredetermined volume of gas, said other member and both spacer elementssettling during such heating and fusing until said other member issupported at said final constant spacing by said lattice arrangement ofoverlapping spacer elements to permit the gas to flow withoutsignificant restriction to substantially all areas of said sealedmembers separated by said spacer elements, said spacer elementspenetrating said layers of dielectric material substantially intocontact with the substrates.

1. A method of sealing flat surfaces of two members in overlyingrelation at a precise preselected distance to create an impermeablechamber of constant height divided into areas by spacer elements that donot significantly impede flow of gas between such areas in the chamber,comprising the steps of providing two substantially transparent flatmembers, each said member having parallel conductors overcoated with athin layer of dielectric material, placing on one of the members aborder of unfused heat-fusible material having a height significantlygreater than said constant height, placing spacer elements ofsubstantially identical thickness in a two-stratum crisscross patternwithin said border to a combined height significantly less than theminimum height of said material, placing the other member with its flatsurface supported on said heat-fusible material, and heating suchassemblage to a temperature above the softening point of said sealingmaterial but below the softening point of the spacer elements to effectfusion of said material and members to create said chamber as, and inconsequence of, said other member settling during such heating andfusing until it is supported at said constant height by saidcrisscrossed arrangement of spacer elements.
 2. A method of making agaseous discharge display device, comprising the steps of providing twosubstantially transparent flat members, each with conductor arraysovercoated with a dielectric material, placing unfused heat-fusiblesealing material over the dielectric material on one of the members as aframe-like border enclosing the major portion of its conductor array,said border having a height substantially greater than the finalconstant spacing desired between said members, disposing two sets ofspacer elements of identical height between the members to create anassemblage in which the elements orthogonally overlap in a lattice-likerelation within the bordered area, elements of one set resting on saidone member and supporting overlying elements of the other set, thecombined thickness of both sets of elements being substantially lessthan the height of said border so that said other member is initiallysupported by the sealing material, and heating the assemblage to atemPerature above the softening point of said sealing material but belowthe softening point of the spacer elements to effect fusion of saidsealing material and members to create an impermeable chamber forconfining a predetermined volume of gas, said other member settlingduring such heating and fusing until it is supported at said finalconstant spacing by said lattice arrangement of overlapping elements topermit the gas to flow without significant restriction to substantiallyall areas of said sealed member separated by said spacer elements. 3.The method according to claim 2, wherein the conductors of each memberare disposed orthogonally to the conductors of the other member, andspacer elements of said one set are disposed equidistant between, andextend parallel to, pairs of adjacent conductors on the said one member,and spacer elements of said other set are disposed equidistant between,and extend parallel to, pairs of adjacent conductors on said othermember.
 4. A method of making a gaseous discharge display device,comprising the steps of providing two transparent flat members, eachwith conductor arrays formed on a substrate and overcoated with a layerof a dielectric material, placing unfused heat-fusible sealing materialover the dielectric material on one of the members as a frame-likeborder enclosing the major portion of its conductor array, said borderhaving a height substantially greater than the final constant spacingdesired between said members, disposing two sets of spacer elements ofidentical height between the members to create an assemblage in whichthe elements orthogonally overlap in a lattice-like relation within thebordered area, elements of one set resting on the layer of said onemember and supporting overlying elements of the other set, the combinedthickness of both sets of elements being substantially less than theheight of said border so that said other member is initially supportedby the sealing material, and heating the assemblage to a temperatureabove the softening point of said sealing material and dielectricmaterial but below the softening point of the spacer elements to effectfusion of said sealing material and members to create an impermeablechamber for confining a predetermined volume of gas, said other memberand both spacer elements settling during such heating and fusing untilsaid other member is supported at said final constant spacing by saidlattice arrangement of overlapping spacer elements to permit the gas toflow without significant restriction to substantially all areas of saidsealed members separated by said spacer elements, said spacer elementspenetrating said layers of dielectric material substantially intocontact with the substrates.